Developmental succession of the microbiome of Culex mosquitoes

Background: The native microflora associated with mosquitoes have important roles in mosquito development and vector competence. Sequencing of bacterial V3 region from 16S rRNA genes across the developmental stages of Culex mosquitoes (early and late larval instars, pupae and adults) was used to test the hypothesis that bacteria found in the larval stage of Culex are transstadially transmitted to the adult stage, and to compare the microbiomes of field-collected versus laboratory-reared mosquitoes.Results: Beta diversity analysis revealed that bacterial community structure differed among three life stages (larvae, pupae and adults) of Culex tarsalis. Although only similar to 2 % of the total number of bacterial OTUs were found in all stages, sequences from these OTUs accounted for nearly 82 % of the total bacterial sequences recovered from all stages. Thorsellia (Gammaproteobacteria) was the most abundant bacterial taxon found across all developmental stages of field-collected Culex mosquitoes, but was rare in mosquitoes from laboratory-reared colonies. The proportion of Thorsellia sequences in the microbiomes of mosquito life stages varied ontogenetically with the greatest proportions recovered from the pupae of C. tarsalis and the lowest from newly emerged adults. The microbiome of field-collected late instar larvae was not influenced significantly by differences in the microbiota of the habitat due to habitat age or biopesticide treatments. The microbiome diversity was the greatest in the early instar larvae and the lowest in laboratory-reared mosquitoes.Conclusions: Bacterial communities in early instar C. tarsalis larvae were significantly more diverse when compared to late instar larvae, pupae and newly emerged adults. Some of the bacterial OTUs found in the early instar larvae were also found across developmental stages. Thorsellia dominated the bacterial communities in field-collected immature stages but occurred at much lower relative abundance in adults. Differences in microbiota observed in larval habitats did not influence bacterial community profiles of late instar larvae or adults. However, bacterial communities in laboratory-reared C. tarsalis larvae differed significantly from the field. Determining the role of Thorsellia in mosquitoes and its distribution across different species of mosquitoes warrants further investigation

Microbiota variations in Culex nigripalpus disease vector mosquito of West Nile virus and Saint Louis Encephalitis from different geographic origins

Although mosquito microbiota are known to influence reproduction, nutrition, disease transmission, and pesticide resistance, the relationship between host-associated microbial community composition and geographical location is poorly understood. To begin addressing this knowledge gap, we characterized microbiota associated with adult females of Culex nigripalpus mosquito vectors of Saint Louis Encephalitis and West Nile viruses sampled from three locations in Florida (Vero Beach, Palmetto Inland, and Palmetto Coast). High-throughput sequencing of PCR-amplified 16S rRNA genes demonstrated significant differences among microbial communities of mosquitoes sampled from the three locations. Mosquitoes from Vero Beach (east coast Florida) were dominated by uncultivated Asaia sp. (Alphaproteobacteria), whereas microbiota associated with mosquitoes collected from two mosquito populations at Palmetto (west coast Florida) sites were dominated by uncultured Spironema culicis (Spirochaetes), Salinisphaera hydrothermalis (Gammaproteobacteria), Spiroplasma (Mollicutes), uncultured Enterobacteriaceae, Candidatus Megaira (Alphaproteobacteria; Rickettsiae), and Zymobacter (Gammaproteobacteria). The variation in taxonomic profiles of Cx. nigripalpus gut microbial communities, especially with respect to dominating taxa, is a potentially critical factor in understanding disease transmission and mosquito susceptibility to insecticides among different mosquito populations

Influence of Nutrients and Integrated Mosquito Management Tactics on Mosquitoes and Their Habitat Microbiomes

Mosquito management in wetlands is complex partly because some of the wetland management operations are known to enhance mosquito production. I aimed to describe the effects of nutrients and integrated mosquito management strategies on mosquitoes produced in wetlands in the following three studies. First, we evaluated the growth characteristics of alkali bulrush (Schoenoplectus maritimus), an alternative aquatic plant of potential bioremediation importance, and its associated mosquito production across a gradient of nitrogen enrichment including the high ammonium nitrogen regimens typically found in constructed wetlands. Mosquito larvae abundance, dominated by the western encephalitis mosquito (Culex tarsalis Coquillett), was significantly greater in enriched versus unenriched mesocosms. Alkali bulrush survived high nitrogen loadings, but its biomass was significantly suppressed at high (>50 mg/liter) ammonium nitrogen concentration in the water. Second, we characterized microbiota associated with C. tarsalis larvae, water column and epibionts of two (alkali and California) bulrushes using 16S rRNA gene sequences generated with Illumina sequencing platform. The diversity of microbiota in mosquitoes sampled from wetlands containing the two bulrushes did not differ appreciably, and was chiefly dominated by Thorsellia (Gammaproteobacteria). The epibionts of the bulrushes and bacterioplankton were dominated by members of Actinobacteria, Bacteroidetes, Cyanobacteria, Proteobacteria and Verrucomicrobia. Overall, nearly 49% of the Bacteria taxa found in the mosquito gut were also found in the habitat, suggesting a strong Culex larvae-Bacteria interaction. Finally, we evaluated the effects of a one-time application of two rates of a key mosquito biopesticide, Bacillus thuringiensis subsp. israelensis (a granular form of VectoBac G) on native microbiota and physicochemical variables in the feeding zone of Culex larvae in experimental mesocosms. Beta diversity of Bacteria communities revealed that samples from low Bti and untreated control mesocosms were significantly separated from high Bti mesocosms and were dominated by unidentified OTU of Cyanobacteria, Cytophagales and Cyclobacteriaceae (Bacteroidetes), and Sphingomonas (Alphaproteobacteria). Phytoplankton (chlorophyll a), sestonic particulates, nutrients, pH and other physicochemical variables in the water column were also significantly reduced in the high Bti mesocosms. Important implications of the results of these studies on integrated mosquito management in aquatic ecosystems are discussed

Influence of Nutrients and Integrated Mosquito Management Tactics on Mosquitoes and Their Habitat Microbiomes

Mosquito management in wetlands is complex partly because some of the wetland management operations are known to enhance mosquito production. I aimed to describe the effects of nutrients and integrated mosquito management strategies on mosquitoes produced in wetlands in the following three studies. First, we evaluated the growth characteristics of alkali bulrush (Schoenoplectus maritimus), an alternative aquatic plant of potential bioremediation importance, and its associated mosquito production across a gradient of nitrogen enrichment including the high ammonium nitrogen regimens typically found in constructed wetlands. Mosquito larvae abundance, dominated by the western encephalitis mosquito (Culex tarsalis Coquillett), was significantly greater in enriched versus unenriched mesocosms. Alkali bulrush survived high nitrogen loadings, but its biomass was significantly suppressed at high (>50 mg/liter) ammonium nitrogen concentration in the water. Second, we characterized microbiota associated with C. tarsalis larvae, water column and epibionts of two (alkali and California) bulrushes using 16S rRNA gene sequences generated with Illumina sequencing platform. The diversity of microbiota in mosquitoes sampled from wetlands containing the two bulrushes did not differ appreciably, and was chiefly dominated by Thorsellia (Gammaproteobacteria). The epibionts of the bulrushes and bacterioplankton were dominated by members of Actinobacteria, Bacteroidetes, Cyanobacteria, Proteobacteria and Verrucomicrobia. Overall, nearly 49% of the Bacteria taxa found in the mosquito gut were also found in the habitat, suggesting a strong Culex larvae-Bacteria interaction. Finally, we evaluated the effects of a one-time application of two rates of a key mosquito biopesticide, Bacillus thuringiensis subsp. israelensis (a granular form of VectoBac G) on native microbiota and physicochemical variables in the feeding zone of Culex larvae in experimental mesocosms. Beta diversity of Bacteria communities revealed that samples from low Bti and untreated control mesocosms were significantly separated from high Bti mesocosms and were dominated by unidentified OTU of Cyanobacteria, Cytophagales and Cyclobacteriaceae (Bacteroidetes), and Sphingomonas (Alphaproteobacteria). Phytoplankton (chlorophyll a), sestonic particulates, nutrients, pH and other physicochemical variables in the water column were also significantly reduced in the high Bti mesocosms. Important implications of the results of these studies on integrated mosquito management in aquatic ecosystems are discussed

Mosquito-microeukaryote interaction study

The data include measurements of mosquito parameters, population dynamics of microeukaryotes, lower trophic microbial (bacteria, small flagellate, etc. ) resources, and organic particle dynamics used to test mosquito-micoreukaryote interaction hypotheses in three microcosm experiments

Data from: Aquatic microfauna alter larval food resources and affect development and biomass of West Nile and Saint Louis encephalitis vector Culex nigripalpus (Diptera: Culicidae)

Ciliate protists and rotifers are ubiquitous in aquatic habitats and can comprise a significant portion of the microbial food resources available to larval mosquitoes, often showing substantial declines in abundance in the presence of mosquito larvae. This top-down regulation of protists is reported to be strong for mosquitoes inhabiting small aquatic containers such as pitcher plants or tree holes, but the nature of these interactions with larval mosquitoes developing in other aquatic habitats is poorly understood. We examined the effects of these two microbial groups on lower trophic level microbial food resources, such as bacteria, small flagellates, and organic particles, in the water column, and on Culex larval development and adult production. In three independent laboratory experiments using two microeukaryote species (one ciliate protist and one rotifer) acquired from field larval mosquito habitats and cultured in the laboratory, we determined the effects of Culex nigripalpus larval grazing on water column microbial dynamics, while simultaneously monitoring larval growth and development. The results revealed previously unknown interactions that were different from the top-down regulation of microbial groups by mosquito larvae in other systems. Both ciliates and rotifers, singly or in combination, altered other microbial populations and inhibited mosquito growth. It is likely that these microeukaryotes, instead of serving as food resources, competed with early instar mosquito larvae for microbes such as small flagellates and bacteria in a density-dependent manner. These findings help our understanding of the basic larval biology of Culex mosquitoes, variation in mosquito production among various larval habitats, and may have implications for existing vector control strategies and for developing novel microbial-based control methods

Independent evaluation of Wolbachia infected male mosquito releases for control of Aedes aegypti in Harris County, Texas, using a Bayesian abundance estimator.

Among disease vectors, Aedes aegypti (L.) (Diptera: Culicidae) is one of the most insidious species in the world. The disease burden created by this species has dramatically increased in the past 50 years, and during this time countries have relied on pesticides for control and prevention of viruses borne by Ae. aegypti. The small number of available insecticides with different modes of action had led to increases in insecticide resistance, thus, strategies, like the "Incompatible Insect Technique" using Wolbachia's cytoplasmic incompatibility are desirable. We evaluated the effect of releases of Wolbachia infected Ae. aegypti males on populations of wild Ae. aegypti in the metropolitan area of Houston, TX. Releases were conducted by the company MosquitoMate, Inc. To estimate mosquito population reduction, we used a mosquito abundance Bayesian hierarchical estimator that accounted for inefficient trapping. MosquitoMate previously reported a reduction of 78% for an intervention conducted in Miami, FL. In this experiment we found a reduction of 93% with 95% credibility intervals of 86% and 96% after six weeks of continual releases. A similar result was reported by Verily Life Sciences, 96% [94%, 97%], in releases made in Fresno, CA